About 20 people have been forced out of their homes and up to 150 properties could be affected.

So what are the issues facing residents and what could happen next?

Image copyrightGoogleImage caption
Ystalyfera is situated in a valley, meaning many houses are built on steep hills

Lay of the land

As is typical in the Welsh valleys, many homes in Ystalyfera are built into the hillside.

About 3,000 people live in the village and it was once home to several mines.

Pwllback Colliery, Varteg Colliery, Tirbach Slanta and Taneri Colliery in neighbouring Godrergraig were among the mines dug in and around Ystalyfera.

Neath Port Talbot Council leader Rob Jones said the "whole area has a legacy of geographical faults - it is a heritage of the mining industry".

The history

Council records show landslides and boulder falls have dogged the area for 120 years.

The first documented case was in January 1897 when a landslide was noted on a geological map.

Since then, there have been at least 45 recorded incidents, including roads being blocked, homes being damaged and, in May 1965, a house and lorry was engulfed on Graig Road.

This is not the complete picture as there were no records kept from November 1986 to December 2012.

However, in that month, thousands of tonnes of rock, soil and trees slipped down the hillside behind the homes, followed by a further two landslides this year, causing some gardens to drop away.

Mr Jones has admitted it is impossible to predict when or where the next landslide will happen.

Image copyrightJohn EmeryImage caption
Eight of the 10 affected properties on Cyfyng Road are now empty

What will happen to the houses?

When the council evacuated people from 10 homes - numbers 81 to 96 - on Cyfyng Road, they were told there was an "imminent risk" to their lives.

The council has admitted there is "no engineering solution" for them, but two households have refused to budge.

The other two were derelict and it is one of these which has been earmarked to be pulled down. One group who left their home are still in a B&B but the council said they were in the process of moving into appropriate accommodation.